Sinusoidal AC Voltage Research Articles

Dynamic Response of Alternating-Current-Driven Light-Emitting Diodes Based on Hybrid Halide Perovskites

In this work, we report the dynamic response of alternating-current-driven light-emitting diodes based on a range of hybrid halide perovskites. Electroluminescence (EL), which appears only in the positive section of a dc voltage, arises in both cycles under a sinusoidal ac voltage. Appearance of EL emission in negative cycles of the ac voltage is explained in terms of available residual charges injected in the previous positive cycle of the sinusoidal voltage; the relative intensity of EL emission in the negative cycle can be correlated to the ambipolarity of charge carriers in the ${\mathrm{CH}}_{3}{\mathrm{NH}}_{3}{\mathrm{Pb}\mathrm{Br}}_{x}{\mathrm{I}}_{3\text{\ensuremath{-}}x}$ series. At low frequencies of the ac voltage, the dynamic response of EL emission in any cycle is in phase with the applied ac voltage; interestingly, the EL emission starts to lag the sinusoidal voltage at higher frequencies. The phase lag also has a correlation to the ambipolarity of the active perovskite material. Finally, the frequency dependence of EL emission under an ac voltage provides the limiting frequency of device operation (\ensuremath{-}3 dB frequency) and thereby the effective carrier mobility in the active heterostructure.

Study on dielectric barrier discharge in nanostructured electrode materials

In order to conduct dielectric barrier discharge experiments under normal pressure and low voltage (less than 15000V), an ac high-voltage differential power supply based on series-parallel LCC-type(Inductor L and capacitor Cr, Cp are connected in series and parallel structure) resonant converter is designed. The designed power supply prototype has the advantages of small size, light weight and easy operation. The power supply prototype has been tested on loads for many times. Its output repeatability is good and it can continuously output stable sinusoidal ac voltage. At the same time, the prototype also has a strong ability to resist electromagnetic interference. Moreover, the dielectric barrier discharge experiment is carried out using copper electrode with zinc oxide nanowires and copper electrode without zinc oxide nanowires. The experimental results show that the starting voltage of the test group with nanostructures growing on the surface is smaller, about 2500V lower than that of the latter under the same dielectric conditions and discharge spacing. In terms of the discharge phenomenon, the former has a better discharge process consistency, the non-nanostructured electrode discharge is unstable, and the difference in the discharge process is obvious.

Design of constant output voltage DC-AC inverter for batteryless solar PV system

This paper introduces a DC-AC inverter design that operates stand alone to deliver power from solar photovoltaic (PV) to the load directly without going through the battery. In batteryless solar PV, the output voltage of solar PV always varies according to solar irradiation, temperature, so that it becomes a challenge in modelling DC-AC inverter with constant output voltage. The design consists of a boost converter, h-bridge switching and driver, and LC filter to generate sinusoidal ac voltage as output to load. To ensure a constant inverter output voltage, the design equipped by a close loop PI controller based on voltage control mode. The design modelled and simulated by PSIM. PV dc input was set variation according to the irradiation value (W/m2) and the output connected to a load that has rated voltage of 220 Vac and 3.4 A of nominal current. The results show that in the irradiation variation 600-1500 W/m2, the inverter was able to maintain the output voltage of 220 Vac ± 0.91%, 50 Hz which is still in the voltage range based on standard. The efficiency produced by DC-AC inverter 97.7 % at 600 W/m2 and 83.6 % at 1500 W/m2.

A Novel Transformerless Single-Stage Grid-Connected Solar Inverter

A novel tranformerless single-stage grid-connected solar inverter with a combination of a bidirectional dc/dc boost converter followed by a flyback inductor inverter is proposed. The inverter shares a common ground with the photovoltaic (PV) panel and the grid, which realizes a zero leakage current and it is the most desired feature in transformerless inverters. Further, the proposed inverter provides the boost voltage operation, hence it does not require a second stage which decreases the system cost and increases the system reliability. The other advantage of the proposed inverter is that it provides both the symmetrical positive voltage gain and negative voltage gain, which allows to use simple sinusoidal pulsewidth modulation technique for realizing the ac sinusoidal output voltage. The proposed inverter steady-state operation and the design equations are presented in detail. The converter dynamic model is developed using state-space averaging approach, and a proportional resonant current controller is designed for inverter closed-loop operation with the grid. The presented analysis and the design are verified with both the simulation and experimental results.

Analisis Pengaturan Parameter Sinusoidal Pulse Width Modulation pada High Precission Closed Loop Full Bridge Bipolar Inverter untuk Pembangkit Tegangan Tinggi Berfrekuensi Tinggi

The application of high voltage becomes more important and wider. High voltage is needed in the process of reducing air contaminants, waste treatment, sanitation, disinfecting microorganisms, testing for insulating high voltage equipment, and transmitting electrical energy. The problem of high voltage AC generation system is still in a large scale, static, not portable, and very expensive. This paper presents an analytical design of a high-voltage AC high-frequency based on power electronic. It is portable, less expensive, and eaasier to control the amplitudo and frequency. The application of the Full Bridge Bipolar Inverter topology with the Sinusoidal Pulse Width Modulation switching method provides variable sinusoidal AC voltage outputs (Vo) on its amplitude and frequency. The Tesla Coil Transformer amplifies the amplitude in accordance with the classification of the high voltage AC in the order of Kilo Volt. The Closed Loop control system in the Bipolar Inverter Full Bridge topology provides high accuracy results between the given setting values and the actual amplitude output and the expected high-frequency AC voltage. Analysis of the SPWM switching pattern parameter settings shows stability for several loading variations

Effects of Frequency and Temperature on Electric Field Mitigation Method via Protruding Substrate Combined with Applying Nonlinear FDC Layer in Wide Bandgap Power Modules

Our previous studies showed that geometrical techniques including (1) metal layer offset, (2) stacked substrate design and (3) protruding substrate, either individually or combined, cannot solve high electric field issues in high voltage high-density wide bandgap (WBG) power modules. Then, for the first time, we showed that a combination of the aforementioned geometrical methods and the application of a nonlinear field-dependent conductivity (FDC) layer could address the issue. Simulations were done under a 50 Hz sinusoidal AC voltage per IEC 61287-1. However, in practice, the insulation materials of the envisaged WBG power modules will be under square wave voltage pulses with a frequency of up to a few tens of kHz and temperatures up to a few hundred degrees. The relative permittivity and electrical conductivity of aluminum nitride (AlN) ceramic, silicone gel, and nonlinear FDC materials that were assumed to be constant in our previous studies, may be frequency- and temperature-dependent, and their dependency should be considered in the model. This is the case for other papers dealing with electric field calculation within power electronics modules, where the permittivity and AC electrical conductivity of the encapsulant and ceramic substrate materials are assumed at room temperature and for a 50 or 60 Hz AC sinusoidal voltage. Thus, the big question that remains unanswered is whether or not electric field simulations are valid for high temperature and high-frequency conditions. In this paper, this technical gap is addressed where a frequency- and temperature-dependent finite element method (FEM) model of the insulation system envisaged for a 6.5 kV high-density WBG power module will be developed in COMSOL Multiphysics, where a protruding substrate combined with the application of a nonlinear FDC layer is considered to address the high field issue. By using this model, the influence of frequency and temperature on the effectiveness of the proposed electric field reduction method is studied.

Application of a Langmuir probe AC technique for reliable access to the low energy range of electron energy distribution functions in low pressure plasmas

The electron energy distribution function (EEDF) in low pressure plasmas is typically evaluated by using the second derivative d2I/dV2 of a Langmuir probe I–V characteristic (Druyvesteyn formula). Since measured probe characteristics are inherently noisy, two-time numerical differentiation requires data smoothing techniques. This leads to a dependence on the employed filtering technique, and information particularly in the region near the plasma potential can easily get lost. As an alternative to numerical differentiation of noisy probe data, a well-known AC probe technique is adopted to measure d2I/dV2 directly. This is done by superimposing a sinusoidal AC voltage of 13 kHz on the probe DC bias and performing a Fourier analysis of the current response. Parameters such as the modulation amplitude (up to 1.5 V) and the number of applied sine oscillations per voltage step of the DC ramp are carefully chosen by systematic parameter variations. The AC system is successfully benchmarked in argon and applied to hydrogen plasmas at a laboratory inductively coupled plasma experiment (4–10 Pa gas pressure, 300–1000 W RF power). It is shown that the EEDF is reliably accessible with high accuracy and stability in the low energy range. Hence, a trustworthy determination of basic plasma parameters by integration of the EEDF can be provided.

Influence of Charge Transport Layers on Capacitance Measured in Halide Perovskite Solar Cells

Summary Capacitance-based techniques have been used to measure the electrical properties of halide perovskite solar cells (PSCs) such as defect activation energy and density, carrier concentration, and dielectric constant, which provide key information for evaluating the device performance. Here, we show that capacitance-based techniques cannot be used to reliably analyze the properties of defects in the perovskite layer or at its interface, because the high-frequency capacitance signature is due to the response of charge carriers in the hole-transport layer (HTL). For HTL-free PSCs, high-frequency capacitance can be considered as the geometric capacitance for analyzing the dielectric constant of the perovskite layer because there is no trapping and de-trapping of charge carriers in the perovskite layer. We further find that the low-frequency capacitance signature can be used to calculate the activation energy of the ionic conductivity of the perovskite layer, but the overlapping effects with charge transport materials must be avoided.

Controller Design and Implementation of Solar Panel Companion Inverters

A solar panel companion inverter (SPCI) is a single-stage dc-ac power converter, installed with each solar panel. Each SPCI synthesizes an ac quasi-square wave voltage with variable pulsewidth. The width of ac output voltage of each SPCI is proportional to available power on the solar panel. Output voltages of SPCIs are aggregated across multiple solar panels connected in series, and a sinusoidal ac voltage is synthesized. In this article, dynamic analysis and closed-loop current controller design of SPCI is presented. Simulation results demonstrating the dynamic response of the closed-loop SPCI are included. The closed-loop current control scheme is implemented on a hardware prototype to demonstrate the grid-tied operation of SPCI, and experimental results are presented. A maximum power point tracking (MPPT) algorithm is implemented for sorted stair-case modulation (SSCM) in MATLAB Simulink. Experimental results demonstrating MPPT operation are presented.

Improved Voltage Harmonics Compensation Strategy for a Stand-Alone DFIG Operating under Unbalanced and Nonlinear Load Conditions

The study presents an improved control and operation for a stand-alone Doubly-Fed Induction Generator (DFIG) energy system under unbalanced and nonlinear load conditions. This type of loads results in unbalance and distorted stator voltage and current at the Point of Common Coupling (PCC), with subsequent power quality degradation and electromagnetic torque pulsations of DFIG. A new and simple control strategy based Proportional-Resonant Controllers (PRCs) in the stationary reference frame is applied in the Load-Side Converter (LSC) for fully compensate the unbalance and harmonic distortion in the PCC and avoid the torque pulsations of DFIG. As a result, symmetrical and sinusoidal AC voltage is applied to the PCC, which indicates that the Rotor-Side Converter (RSC) can be still controlled with the traditional vector control strategy, to adjust the generator torque and to balance active power. This strategy is conceptually simple, it does not require for rotating coordinate transformation and the sequence decomposition process, in addition no current sensors need to be installed at load or stator side, so that the number of current sensors employed is reduced. Simulation results using MatLab/Simulink are given and show the effectiveness and validity of the proposed control scheme to eliminate the harmonics in the PCC and torque pulsations of DFIG.

High Impedance Fault Detection using Advanced Distortion Detection Technique

A High Impedance Fault (HIF) in the power distribution systems remains mostly undetected by conventional protection schemes due to low fault currents. Apart from degrading the reliability of power supply to customers, HIF can impose a high cost on the utilities due to technical damages. The nonlinear and asymmetric nature of HIF makes its detection and identification very challenging. HIF signatures are in the form of minute-level distortions in the observable AC sinusoidal voltage and current waveforms but these signatures do not follow a clear pattern. In this paper, we present Advanced Distortion Detection Technique (ADDT), based on waveform analytics to distinguish and detect HIF. In addition, the ADDT analysis provides a fair assessment about the location and severity of HIF for efficient decision-making at the DSO level. ADDT is computationally lightweight and can be implemented in actual relays, hence it is enabled to provide an easy and cost-effective solution to HIF detection issues. ADDT robustness is tested in several simulation cases of interest using the IEEE-34 and IEEE-13 distribution test feeder systems in RTDS power system simulator. The test results successfully demonstrate the effectiveness and robustness of ADDT.

Design of a hybrid solar photovoltaic system for Gollis University’s administrative block, Somaliland

This work presents the design of a 100kVA hybrid solar power system for Gollis University’s administrative block, Hargeisa, Somaliland. Prior to the system design, a preliminary field work on the site was performed to essentially measure the power/energy consumption of Gollis university’s administrative block. The results from the site survey was then used to select the appropriate equipment and instrument required for the design. This was achieved by calculating the energy consumption and then sizing the solar panel, battery, inverter and charge controller. The battery back-up time analysis at full load was also carried out to determine the effectiveness of the inverter size chosen. The inverter system was modeled and simulated using the MATLAB/Simulink software package. The simulation was used to study the reliability of the size of inverter chosen for the design, since the failure of most photovoltaic systems is ascribed to inverter failures. The results from the MATLAB/Simulink simulation showed that the inverter selected for the hybrid PV system has the ability to maximize the power produced from the PV array, and to generate sinusoidal AC voltage with minimum output distortion. The results also revealed that the PV solar system can provide a back-up time of 47.47 hours. The implications of the results are then discussed before presenting the recommendations for future works. Â

The effects of applying different bias voltages and phase differences on performance of an asymmetric surface dielectric barrier discharge; an experimental investigation

In the present research, the performance of the electrohydrodynamic force in an asymmetric surface dielectric barrier discharge actuator has been investigated at different bias voltages. The effects of DC, AC plus DC (DC-offset), and sinusoidal bias voltages on the force generation have been studied through measuring the electric wind velocity profiles, surface potential, and electric field. The results showed that applying DC and DC-offset biases to the lower electrode instead of connecting it to the ground in a typical case increased the charge deposition on the dielectric surface and consequently reduced the electrohydrodynamic force generation. This effect was also observed in case of exchanging these voltages with AC sinusoidal voltage of the upper electrode. In addition, as a new idea, two-phase shifted AC voltage was applied to the electrodes and the resulting changes have been studied. The obtained results at 180^{^circ } phase difference were very noticeable and showed 46% improvement in the maximum velocity of the induced flow relative to the grounded electrode with the same input power. Using this technique, a certain wind velocity can be obtained at relatively lower voltages and input powers compared to the conventional case of grounding the lower electrode. Such a capability is significant in aerodynamic applications, where applying large values of the high voltages may disturb the operational systems.

Characteristics of the dielectric barrier corona discharges

In this paper, the electrical characteristics of both the dielectric barrier corona discharge and the usual ac corona discharge have been studied in parallel with the ozone generation under the same operating conditions. Therefore, the corona discharges were formed inside two identical reactors in the form of a coaxial wire-to-cylinder with and without a dielectric barrier covering the inner surface of the cylinder. The two reactors have been fed by constant flow rates from the dry air and the oxygen gas independently at the atmospheric pressure and the room temperature, in parallel with applying a sinusoidal ac voltage to the electrodes of the reactors. The electric power consumed in forming the corona discharges and the waveform of the discharge current as well as the ozone concentration generated in the flowing gases through the reactors have been studied versus the peak of the ac voltage that was applied to the reactors. The current-voltage oscillograms showed that the sequence of the dielectric barrier corona discharge modes in both the dry air and the oxygen gas is the same as the sequence of the usual ac corona discharge modes in the same gases. With the increase of the peak value of the ac voltage applied to the dielectric barrier corona discharge reactor, the peak of the discharge current increases linearly while the value of the electric charge accumulated on the surface of the dielectric barrier increases in the form of a power function. The ozone concentration generated by the dielectric barrier corona discharges is approximately equal to the ozone concentration generated by the usual ac corona discharges in both the dry air and the oxygen gas under the same operating conditions.

Nonisolated Harmonics-Boosted Resonant DC/DC Converter With High-Step-Up Gain

High-step-up dc/dc converters are widely required in grid-connected applications with renewable energy sources. An extremely high-ratio step-up nonisolated dc/dc converter, in the form of a harmonics-boosted resonant converter, is proposed in this paper. This proposed converter consists of a high-frequency dc/ac inverter stage that is followed by a passive ac/dc rectifier stage connected in cascade. Conventionally, such a dc/ac inverter is designed to output a pure sinusoidal ac voltage with an amplitude several times the amplitude of the input voltage. However, for the proposed converter, the harmonics-boosted inverter stage is designed to contain selected voltage harmonics that significantly boost the amplitude of its output voltage. This greatly increases the overall gain of the converter. The adopted ac/dc stage is a diode-capacitor rectifier, which is of high efficiency and easily extendable to increase the voltage gain. Importantly, the proposed converter involves only one active switch. With only one active switch, the driver's loss is minimized and the converter's control is simplified. Zero-voltage switching is applied to reduce the switching loss, which also allows the converter to operate efficiently at high frequency, and thus can be designed for high power density. The optimal design of the two converter stages and their combined voltage gain is investigated and reported. Besides, a design guideline of the proposed converter is provided. A prototype of a 57-time harmonics-boosted resonant converter with 3.3 V input voltage, 500 kHz switching frequency, and 21 W output power, is built. The experimental result shows that the achieved converter's efficiency is as high as 88.6%.

Novel Three-Port Inverter Outputting Two Sinusoidal AC Voltages

—This paper proposes a new three-port, T-type multi-level converter (TPTMC) that simultaneously outputs two sinusoidal AC voltages with different frequencies: 50 Hz and 60 Hz. The proposed TPTMC is composed of a DC voltage source, two T-type power electronic legs, a filter inductor set, a frequency separated transformer (FST), a 60 Hz filter capacitor, a 50-Hz filter capacitor, and a DSP controller. The most salient feature is that the proposed TPTMC outputs two sinusoidal AC voltages with different frequencies using only a power converter. A hardware prototype is developed to verify the performance of the proposed TPTMC. The experimental results are as expected.

Floating harmonic probe measurements in the low-temperature plasma jet deposition system

The floating harmonic probe is a relatively new plasma diagnostic method, which was proposed for applications at conditions when insulating films are deposited on the probe and, consequently, the classical Langmuir probe method fails. In the floating harmonic probe method a purely sinusoidal AC voltage is applied to the probe constructed in a standard manner via a capacitor. From the spectral components of the measured AC probe current waveforms, the electron temperature and the positive ion density can be obtained. In this contribution we present the comparison of the electron temperature and density acquired by the floating harmonic probe method with those obtained by the classical Langmuir probe. The experiments are performed in the flowing DC discharge in argon. In addition, the results from the floating harmonic probe method obtained during deposition of an insulating iron oxide thin film are shown. All the data is complemented by the qualitative discussion.

Dielectrophoresis-based multi-step nanowire assembly on a flexible superstrate

Nanowire assembly based on dielectrophoresis (DEP) could be a useful and efficient tool for fabricating nanowire-based devices. Although there have been extensive reports on the DEP nanowire assembly, the new approaches that make DEP more facile and affordable are still desirable. Herein, we present an approach using the reusable electrodes to assemble silver nanowires onto a removable, independent polyethylene terephthalate (PET) film. The PET film is placed on the reusable electrodes, and a sinusoidal AC voltage is applied to the electrodes to induce DEP force for nanowire assembly upon the flexible film. We explore the influences of voltage, frequency and film thickness on nanowire assembly and further realize the assembly of silver nanowire arrays. In addition, the induced electric field is rotated in two consecutive steps to assemble the rectangular mesh-like nanowire networks. This reusable and facile approach for DEP nanowire assembly could provide a low-cost, precise, rapid and convenient tool for applications in the fields of flexible electronics.

Experimental Challenges when Measuring Partial Discharges under Combined DC and High Frequency AC Voltage

The present paper reviews some of the challenges involved in designing and building an experimental setup for measurement of partial discharge under combined AC and DC voltage. A design of a modular test cell is discussed, as well as all parameters relevant to proper control of the experiment conditions. The described experimental setup is capable of producing sinusoidal AC voltage at a variable frequency up to 5 kHz superimposed a high DC voltage. The challenges related to intermittent noise reduction was remedied by placing the setup in a Faraday cage and controlling the setup from the outside by optical cables. All equipment in the test setup was connected to the power grid through low-pass filters.

Operational performance stability of grid-connected photovoltaic generator via DC–DC converter and 48-pulse voltage source inverter

This paper presents detailed steady-state stability analysis of PV generator interfaced to grid via DC–DC buck–boost converter, 48-pulse DC–AC sinusoidal Voltage Source Inverter (VSI), LC filter and transmission line. The main purpose of the DC–DC converter implementation is to inject the voltage corresponding to the Maximum Power Point of the PV generator. 48-pulse VSI is chosen as the harmonic contents in the output voltage are far away from the fundamental frequency with very small magnitudes. For numerical simulations, the complete nonlinear dynamical mathematical model in dq stationary reference frame is used including that of the terminal characteristics of the PV generator. The study comprises eigenvalues of the linearized model at various solar intensities. The robustness of the system operating point is checked by time domain simulations after small perturbations in the gird voltage and step changes on the solar insolations. Historically, series compensation of transmission lines has been used to increase the power transfer capability of the power system. In this study, the impact of equipping the transmission line with series capacitor on the system performance is highlighted. Furthermore, the effect of partial shading of the PV modules on the stability of the proposed power plant is investigated.